1. Field of the Invention
The present invention relates to aqueous compositions containing a mixture of polyurethane/urea resins containing alkoxysilane groups and water reducible oligomers containing alkoxysilane groups, and to coatings, sealants and adhesives prepared from these compositions that have improved solvent resistance.
2. Description of the Prior Art
The production of linear or cross-linked aqueous polyurethane-urea dispersions is known as shown by U.S. Pat. Nos. 3,479,310; 4,066,591; 4,092,286; 4,108,814; 4,237,264; and 4,238,378 which disclose linear polyurethane-ureas and U.S. Pat, Nos. 3,870,684, 4,203,883 and 4,408,008, which disclose cross-linked polyurethane-ureas. The aqueous polyurethane-urea dispersions may be used for a wide range of commercial applications such as adhesives or coatings for various substrates including textile fabrics, plastic, wood, glass fibers and metals. Chemical resistance, abrasion resistance, toughness, tensile strength, elasticity and durability are among the many desirable properties of these coatings.
U.S. Pat. No. 5,859,118 and copending applications, U.S. Ser. Nos. 08/992,163 and 08/992,551, are directed to the production of aqueous polyurethane/urea dispersions containing alkoxysilane groups. While it is disclosed that coatings prepared from these dispersions have improved solvent resistance, it is generally necessary to cure these coatings at elevated temperatures to obtain optimum solvent resistance. Coatings cured at room temperature do not obtain optimum solvent resistance.
Accordingly, it is an object of the present invention to improve the solvent resistance of coatings cured under ambient conditions, while retaining the other valuable properties of coatings prepared from aqueous polyurethane/urea dispersions.
This object may be achieved in accordance with the present invention by blending the aqueous polyurethane/urea dispersions containing alkoxysilane groups with water reducible oligomers containing alkoxysilane groups as described hereinafter.
Aqueous polyurethane dispersions containing alkoxysilane groups are also disclosed in U.S. Pat. Nos. 5,041,494, 5,354,808 and 5,554,686. However, none of the proceeding patents and copending applications disclose that the solvent resistance of coatings obtained from these dispersions could be improved by incorporating water reducible oligomers in accordance with the present invention.